In the related art, as an offset sheet-fed printing ink, an ultraviolet curable ink which is cured by irradiating an ultraviolet ray is used. Further, as an adhesive agent around a flat panel display (FPD) such as a liquid crystal panel or an organic electro luminescent (EL) panel, an ultraviolet curable resin is used. In order to cure the ultraviolet curable ink or the ultraviolet curable resin, generally, an ultraviolet ray irradiating device which irradiates an ultraviolet ray is used.
A lamp type irradiating device which uses a high pressure mercury lamp or a mercury xenon lamp as a light source is known as the ultraviolet ray irradiating device in the related art. In recent years, due to demands on reduced power consumption, elongated life-span, and compact device size, an ultraviolet ray irradiating device using an LED as a light source, instead of a discharge lamp of the related art has been developed (for example, see Patent Document 1).
The ultraviolet ray irradiating device disclosed in Patent Document 1 includes a base plate in which a plurality of light emitting elements is two-dimensionally disposed, a reflective tube (mirror unit) which is provided to enclose the base plate to guide the ultraviolet ray emitted from the light emitting elements, and a cooling unit which cools the base plate. Further, the ultraviolet ray is mixed by the reflective tube, so that a uniform irradiating distribution is obtained in an irradiating area. Further, when an LED is used as a light source, most of the supplied power is converted into heat so that the luminous efficiency and the lifespan are lowered due to the heat generated by the LED. Therefore, the ultraviolet ray irradiating device disclosed in Patent Document 1 employs a configuration which suppresses the heat generation of the LED by a cooling unit such as a heat sink.